1. Field of the Invention
The present invention generally relates to burst testing of pressure vessels and, more particularly, is concerned with a apparatus and method for pressure burst testing of a hollow vessel by mechanically applying pressure thereon.
2. Description of the Prior Art
In the course of manufacturing any pressure vessel which ultimately will be placed in the hands of or physical presence of human beings, certain minimum safety standards must be adhered to. The standards now established by ASME-Boiler and Pressure Code "An American National Standard"--Section V entitled "Nondestructive Examination"--dated July 1, 1983 require that varying safety standards (expressed as safety factors) must be met by any manufacturer prior to any product being issued for actual use. These safety standards may cover operation or use of the supplied product in diverse environments (temperature, humidity, rapidity and range of changes in both) and under varying pressures applied at varying rates of pressure increases and decreases. Impact and vibration effects may also be factors in meeting minimum performance standards.
This diverse array of conditions for replicating actual use situations has more or less been reproduced successfully and satisfactorily for most pressure vessel product testing by the manufacturers involved, using the same pressure applying medium as would be used in the actual application of the product. However, in the case of a pressure vessel or chamber, which is pressurized by an explosive charge, particularly a "designed for one time use only" vessel, i.e., gun barrel, satisfactory results are yet to be reached due to several drawbacks.
One drawback is that actual testing at required-use pressures stresses the product sufficiently to make it unusable for the once-only application it was designed for. Another drawback is that "pressure over specified rate and time" static type tests are difficult, if not impossible, to manage consistently when using explosives. Hydrostatically replicated pressure building involves expansion/leak problems, problems of contamination with a medium of porous or laminated composite materials used in the product being tested, and problems of shrapnel-like reactions when the product fails catastrophically under test load. Still another drawback is that explosive-generated pressures are exceedingly dangerous in the areas of actual test (again, shrapnel generation upon failure), test procedure setup (explosives loading and arming), handling, shipping, and transferring of explosive materials. A further drawback is that explosive pressure generation for test purposes, particularly under requirements of a multi-environment/multi-test program, is economically prohibitive in that testing costs could easily exceed the product's base value many times over. Also, excessive insurance and special facility costs would also be factors of consideration.
This particular field of pressure generation (such as by explosives) has in the last decade fallen far short of the needs of manufacturers who are now working with exotic materials and materials processes which are oftentimes very costly and likewise time consuming to produce. This is particularly the case in armament development and related technology. A demand has resulted for a nondestructive, repeatable, reliable, consistent, controllable, and economical method of replicating explosively generated pressures within varying designs of vessels or vessel-like chambers. Prior art techniques of pressure testing vessels, i.e. gun and cannon barrels and breaches, such as represented by the methods and apparatuses disclosed in U.S. Pat. Nos. to Von Boutteville et al (3,863,499), Seyd et al (3,919,880), Brown et al (4,263,807), Betts (4,356,720) and Gentiluomo (4,419,881), have failed to meet this urgent need.